1. Field of the Invention
The present invention relates in general to an oil pick-up device of a compressor such as a refrigeration tube of the, device to an oil pick-up device which reduces noise by providing an annular protrusion on a cylindrical oil pick-up tube of the device.
2. Description of the Prior Art
Conventionally, domestic or commercial refrigerators have used CFC-12 (Chlorofluorocarbon 12) as a refrigerant. As known by those skilled in the art, there have been proposed and manufactured several types of refrigeration compressors for the refrigerant, CFC-12, with a desired level of noise and operational performance as a result of prolonged improvement of refrigeration technology. However, CFC-12 is known to cause destruction of the ozone layer of the atmosphere and there is the recent trend of limitation of use of CFC-12. Hence, it is required to newly develop a refrigerant, such as HFC-134a (Hydrofluorocarbon 134a), substituting for CFC-12 and design a compressor for the newly-developed refrigerant. On the other hand, the refrigeration compressors require to be provided with refrigeration oil, a kind of lubricant, irrespective of kinds of the refrigerants. It is noted that the refrigeration compressor using HFC-134a should be provided with newly-developed refrigeration oil which agrees with intrinsic characteristics of HFC-134a.
In order to supply the refrigeration oil for drive parts, such as a crankshaft, of the refrigeration compressor, this compressor is generally provided with an oil pick-up device. There have been proposed several types of oil pick-up devices as depicted in FIGS. 1A to 1C, 2 and 3. With reference to these drawings, the known oil pick-up devices include individual inclined oil pick-up tubes 12, 12a, 12b and 12c each of which is fixed to the bottom center of a crankshaft 14 of the compressor. Here, the tube 12 of FIGS. 2 and 3 has a longitudinal slot 10 and a protruded flap 15 covering a part of the slot 10. The other tubes 12a to 12c having no slot and somewhat different constructions of air exhaust ports 11 and protruded flaps 13 and 17, nevertheless have something in common with the protruded flaps.
Hereinbelow, the operational effect of the known oil pick-up devices will be described with reference to the embodiment of FIGS. 2 and 3.
In operation of the compressor, the rotation of the crankshaft 14 makes the oil pick-up tube 12 be rotated in a direction of the arrow of FIGS. 2 and 3. This causes the refrigeration oil, into which the lower part of the tube 12 is submerged, to ascend the outer surface and inner space of the tube 12 due to the intrinsic viscosity of the oil, as well as the centrifugal force generated by the rotation of the tube 12. When the refrigeration oil ascends the outer surface of the tube 12 as described above, the oil runs against the protruded flap 15 and is scattered. This flap 15 is designed to produce an additional function of interception of foams of the refrigeration oil.
However, when this known tube 12 is rotated in the direction of the arrow of FIGS. 2 and 3, there is a pressure difference in the tube 12 in such a manner that the pressure at the part A is higher than that of the part B. This oil pick-up device thus has a problem in that such a pressure difference causes generation of noise and prevents the interception of foams of the oil when the oil is scattered on the flap 15.
Japanese Patent Publication No. Sho. 63-16588 disclosed a known hermetic compressor having another type of oil pick-up device. As depicted in FIG. 4, this hermetic compressor includes a shielding plate 23 for blocking a bottom opening of a crankshaft bearing 18. This shielding plate 23, which is arranged as spaced from and facing a lower end of the crankshaft 9, has a center through hole 24 for introducing the refrigeration oil 19 into the crankshaft 9. The compressor further includes a pump case 21 which is fitted on the lower end of the crankshaft 9 and has a downwardly protruded oil inlet pipe 22. This inlet pipe 22 is inserted into the center through hole 24 of the plate 23.
The shielding plate 23 divides the inner space of the crankshaft bearing 18 into two parts, i.e. , upper and lower parts. In this respect, when the refrigeration oil introduced into the upper part of the inner space is rotated by the rotation of the pump case 21 due to the rotation of the crankshaft 9, the rotational force generated in the upper part of the inner space is prevented from being transferred to the refrigeration oil 19 remaining in an oil reservoir. Hence, the surface of the refrigeration oil 19 below the shielding plate 23 descends for the moment lower than the level of the pump case 21 and this generates, even when the oil surface returns to its initial level, no vortex flow at the inlet pipe 22 of the case 21 due to centrifugal force generated at the outside part 21a of the case 21. Accordingly, it is possible to prevent the inlet pipe 22 of the case 21 from having negative pressure. The oil 19 is thus smoothly introduced into an eccentric conduit 20b of the crankshaft 9 and this causes smooth oil supply for the crankshaft 9 as well as prevention of sticking of the bearing 18 to the crankshaft 9. However, this type of oil pick-up device has a problem in that it generates vibration and noise, and furthermore, does not intercept the oil foams which are to be introduced into the upper part of the inner space of the shielding plate 23 through the inlet pipe 22 and the center through hole 24.